1. Field of the Invention
The present invention relates to an edge connector having at least one electroplated electrical terminal and to a method for manufacturing such an edge connector.
2. Background Art
An edge connector is a connector having at least one electrical terminal arranged along one side of its printed board. The electrical terminal is connected to an electronic circuit on the printed board by an electrical conductor formed on the board. The edge of the printed board on which the electrical terminal is disposed constitutes an edge of the edge connector, and is referred to as the “connector edge.” The connector edge is inserted into a slot provided, e.g., on a motherboard. This slot is called an “edge connector adapter.”
The insertion of the connector edge into the edge connector adapter results in the contact of the electrical terminal of the edge connector with a terminal mounted in the edge connector adapter. (This terminal of the edge connector adapter is later referred to as an “inter-terminal member.”) As a result, the electronic circuit disposed on the printed board of the edge connector (hereinafter referred to as a “first electronic circuit) is electrically connected to an electronic circuit on the substrate or motherboard, etc. on which the edge connector adapter is disposed (hereinafter referred to as a “second electronic circuit), thereby allowing the exchange of electrical signals between these electronic circuits.
Incidentally, the edge connector may be inserted into and withdrawn from the edge connector adapter a plurality of times. (The cycle of such insertion and withdrawal of the edge connector is hereinafter referred to simply as the “mating/unmating cycle.”) Therefore, the specifications of the edge connector include the maximum allowable number of mating/unmating cycles, or mating/unmating durability. The mating/unmating durability of an edge connector depends primarily on the mating/unmating characteristics of its electrical terminal. Typically, the electrical terminal is plated to ensure sufficient mating/unmating durability of the edge connector. In such a case, it is common to use electroplating, since this method of plating is simple and low cost and allows deposition of a thick plating having good adhesion.
An electroplating method is described, e.g., in Japanese Laid-Open Patent Publication No. 2005-322868. Other prior art includes Japanese Laid-Open Patent Publication Nos. 10-261598 (1998), 2002-164704, and 2006-41226.
Electroplating the electrical terminal requires an electric current to be supplied to the terminal after immersing it in a plating solution. In many cases a plating electrode and a lead wire or conductor for electroplating are provided on the printed board to accomplish this purpose. More specifically, the lead conductor for electroplating is connected at one end to the electrical conductor connected between the electrical terminal and the electronic circuit of the edge connector. The other end of the lead conductor is connected to the plating electrode. With this connection, a voltage is applied to the plating electrode to electroplate the electrical terminal.
After completion of the electroplating, the portion of the printed board having the plating electrode thereon is severed together with a portion of the lead conductor to reduce the size of the edge connector. The resulting printed board of the edge connector includes the remaining portion of the lead conductor. It has been found, however, that when such an edge connector is used for transmission of high frequency electrical signals, this remaining portion of the lead conductor acts as an open stub, thereby adversely affecting or degrading the signals.
To avoid this problem, the electrical terminal may be electrolessplated, instead of being electroplated, since electrolessplating does not require any lead conductor for plating. However, electrolessplating is disadvantageous in that the plating deposition rate is slow, with the result that it takes a long time to deposit a plating of the desired thickness, thus lowering the productivity. Further, electrolessplating is relatively high in cost as compared to electroplating, since the solution for electrolessplating need be frequently replaced. Furthermore, generally, plating deposited by electrolessplating has lower adhesion than plating deposited by electroplating, limiting and reducing the mating/unmating durability of the edge connector.
Thus, electrolessplating of electrical terminals is accompanied by problems such as lower productivity, increased cost, and decreased mating/unmating durability.
On the other hand, the lead conductor for electroplating may be shortened to avoid degradation of the electrical signals transmitted through the electrical conductor. Shortening of the lead conductor may be achieved by extending it toward the connector edge of the printed board, instead of toward any other edge of the printed board. However, it is necessary that no components (i.e., terminals, etc.) be present within a predetermined distance from the connector edge toward the center of the printed board. (This peripheral margin region is referred to as a “clearance.”) As a result, the lead conductor for electroplating cannot be extended toward the connector edge of the printed board.
This means that the lead conductor for electroplating must be extended from the electrical conductor or electrical terminal to an edge of the printed board other than the connector edge. (This edge is spaced a greater distance from the electrical conductor and electrical terminal than is the connector edge.) Electroplating is performed by applying a voltage to such a lead conductor through a plating electrode on the printed board. The portion of the printed board on which the plating electrode is disposed is subsequently removed after completion of the electroplating, as described above. This means that it is difficult to make the lead conductor short enough not to degrade the electrical signals transmitted through the electrical conductor.